searching for a low power DSP, about 80 MIPS with flash and A/D's

Started by Fonze September 3, 2003
Hi Fonze

Actually the SPI protocols are similar except that in true SPI the
clocks halt when the /CS (Frame Synch) is inactive.  If this is
important, you can manualy manipulate the FS/CLK lines by directly
writing to these pins as bit IO at a rate up to F/2 or 37Mb/s for the 75
MIP VC33-150 (the serial port still works even though the pins are
configured for IO). Another option is to use the DMA to 'burp out' the
FS/CLK pattern you want.  Clock, frame and data polarity, edge
selection, idle hi/lo etc... are then just configuration bits in the
serial port.

You may also find that if your SPI devices have /SS pins, they will go
high-Z when not selected.  This would then allow you to hang multiple
devices on one serial port.

Otherwise, you are right... there is only one serial port.

One word of caution regarding programmable IO. Resist the temptation to
directly tie the FSX/FSR CLKX/CLKR lines together.  Being programmable,
IO pins are easily misconfigured or power up in undesired modes.  Taje
notice of the fact that most programmable IO on devices like the VC33 do
not come with hardwired and therefor purely combinatorial hi-z pins.
The solution is simply to add a small series resistor.  A side benefit
is that the series resistor also helps to match up the pin driver Z-out
to the transmission line so you end up with cleaner signals :-)

Best regards,
Keith Larson
Fonze wrote:

Hi Keith,

Thank you very much for your enthusiasm.

I had a glance to your TMS320VC33. It could effectively be quite easier
to develop my application in floating point, and the TMS320VC33 would be
perfect for this. The problem is it has no peripherals as SPI ports,
just one serial.

Best regards

|Keith Larson                              |
|Member Group Technical Staff              |
|Texas Instruments Incorporated            |
|                                          |
| 281-274-3288                             |
|                         |
|     TMS320C3x/C4x/VC33 Applications      |
|                                          |
|                                          |
|               TMS320VC33                 |
|    The lowest cost and lowest power      |
|    floating point DSP on the planet!     |
|              500uw/Mflop                 |